This invention relates to a catheter assembly, and more specifically, to a catheter assembly which is used by inserting in a blood vessel.
Typical balloon catheters for insertion into a blood vessel such as catheters for PTCA (percutaneous transluminal coronary angioplasty) (hereinafter referred to as PTCA catheters) are provided with a lumen for guidewire passage formed along its full length in addition to the balloon inflating/deflating lumen. In the use of such catheters, the guidewire is preliminarily inserted in the guidewire passage lumen of the catheter before the catheter insertion into the blood vessel, and the catheter and the guidewire are simultaneously advanced within the blood vessel with the guidewire ahead of the catheter until their distal ends reach the target site, namely, around the stenosis in the blood vessel.
This operation is very difficult, and a considerable skill was required to succesfully complete such operation. As shown in FIG. 12, in a typical process, a guiding catheter 5 accommodating a guidewire 2 and a catheter 3 is inserted into the blood vessel 9. Then the guiding catheter 5 is advanced in a blood vessel 9 until the distal end of the guiding catheter 5 reaches the entrance or a narrow blood vessel. The guidewire 2 and the catheter 3 provided with the balloon 36 are then advanced along the narrower blood vessel one after another until they reach near the stenosis lesion. The guidewire 2 is advanced to extend through and beyond the stenosis 10, and the catheter 3 is advanced along the guidewire 2 until the balloon 36 of the catheter 3 is positioned right within the stenosis 10. The balloon 36 is then inflated to dilate the stenosis 10. Such complicated operation must be conducted at the proximal extracorporeal end of the catheter by groping. Therefore, the structure, and hence, the operational convenience of the catheter and the guidewire are of great significance.
A wide variety of PTCA catheters are available for use in the cases of different stenosis sizes and blood vessel diameters, and PTCA catheters of different balloon sizes are also available for step-wise dilatation of the stenosis lesion. In some cases, exchange of the PTCA catheter that has been inserted in the blood vessel may become necessary. Repeated withdrawal and insertion of catheters is also carried out when a plurality of devices called stents are indwelled in the blood vessel for the purpose of maintaining the inner diameter of the blood vessel.
Preferably, such catheter exchange is effected with the guidewire being left in the blood vessel of the patient in order to reduce the burden of the patient, the time and trouble of the operation, and the risk of infection.
As described above, the lumen for guidewire passage in the conventional catheters extends along its full length. Therefore, for effecting catheter exchange by withdrawing the catheter out of the patient's body from the proximal end of the guidewire with the guidewire being retained in the patient's body, it has been necessary for the proximal extracorporeal end of the guidewire to extend beyond the proximal end of the catheter a length longer than the full length of the catheter. The extracorporeal end of the guidewire extending for such a long length has been quite an obstacle in the operation of the catheter.
In view of such situation, U.S. Pat. No. 4,762,129 proposes a catheter wherein the lumen for guidewire passage does not extend through its full length. The guidewire lumen of this patent catheter extends only between the distal end opening and an opening formed on the periphery of the catheter several centimeters proximal from the distal end, and the guidewire proximal of the guidewire lumen extends along the exterior of the catheter. The guidewire and the catheter are in engagement with each other only along the length of such short lumen, and therefore, this catheter can be exchanged while the guidewire is anchored in the patient's body, even if the guidewire protruded from the patient's body by a short length. Such catheter is known as a rapid exchange catheter.
When a catheter having a guidewire inserted through its guidewire lumen is advanced through the blood vessel of a patient to the target site, the guidewire and the catheter should be respectively handled on their extracorporeal ends (for example, on their femoral ends) by pushing and pulling the catheter/guidewire with occasional rotation, and such movement of the catheter/guidewire should be transmitted to their distal ends. Accordingly, the catheter should be provided with sufficient torque transmission and pushability. The catheter should also have a sufficient kink resistance to prevent the blockage of the balloon inflation lumen by folding of the catheter.
However, in the rapid exchange catheter as described above, the rigidity (flexural rigidity and tortional rigidity) of the proximal portion of the catheter in the proximal side of said opening on the periphery (see FIG. 11), where the guidewire is not accommodated in the lumen, was significantly lower than the distal portion of the catheter in the distal side of said opening, where the guidewire is accommodated in the guidewire passage lumen. Due to such insufficiency in the rigidity of the proximal portion of the catheter, the catheter suffered from insufficient kink resistance, and insertion of such rapid exchange catheter into the blood vessel often proved unsuccessful.
Such catheter also suffered from insufficient torque transmission and pushability. One reason for such disadvantage was the play inevitably formed between the guiding catheter 5 and the catheter main segment (shaft) 31 since the guidewire 2 extended along the exterior of the catheter main segment 31 shown in FIG. 11. Another reason was the relatively small outer diameter of the catheter main segment, which was an inevitable consequence of separate accommodation of the guidewire 2 and the catheter main segment 31 within the interior of the guiding catheter 5.